9 - fungi as pathogens Flashcards
What medical problems do fungi cause?
Mycoses - fungal diseases
Allergies
Mycotoxins - toxins produced by fungi
What are true pathogens?
capable of causing disease in healthy persons with no immune defects
What are some features of true pathogenic fungi?
Specifically adapted to survive in high temperature and low oxygen environments
They display thermal dimorphism
Often asymptotic in healthy host
Not obligate parasites
What is thermal dimorphism in true pathogenic fungi?
Fungi are in the hyphae form at temperatures lower that 30 degrees whereas when they are in animals (35 degrees to 40 degrees) they are in the yeast form and are parasitic
Give some examples of true pathogenic fungi?
Histoplasmosis (histoplasma captsulatum) - pneumonia
Coccidioidomycosis (coccidioides immitis) - mostly asymptotic but can cause fevers and lung infections
What are opportunistic pathogens?
Pathogens that only cause disease in people with weaker immune systems
Pathogens that only cause disease in people with weaker immune systems
They have no specific adaptations to the host
Don’t have that much treatment
Give some examples of opportunistic pathogenic fungi?
Candida albicans infection (candidiosis) - a dimorphism yeast that causes systematic infections in immune compromised
Aspergillosis (aspergillus species) - a filamentous fungi found in hot temperatures that produces small spores and causes tissue necrosis in the lungs and sometimes the brain and heart
What sort of infections do dermatophytes cause?
Superficial, non life threatening infections that effect healthy hosts
What are the main control agents of human mycoses (fungal disease) and how do they work?
Azoles and polyenes which both interfere with ergosterol and fluorocystosine which prevents fungi growth
How does amphotericin B work?
Binds to ergosterol, increasing cell membrane permeability and causing cell death
How do necrotrophic pathogens damage plants?
They excrete toxins and enzymes that digest cell walls, cause host cell death and invade tissue.
Give an example of a necrotrophic pathogen?
Armillaria mellea (honey fungus) - causes root rot
How do biotrophic pathogens effect plants?
They don’t kill the host and have limited tissue invasion, they just compromise the plants functions
What are some examples of biotrophic pathogenic fungi?
Puccinia graminis - infect mesophyll cells
Erysiphe graminis - infect epidermial cells
